Battery to battery charger views?

[WotEver]

 

It's not a lot, I am sure. I have a swankey Sterling charger and an undersized gennie. The gennie won't work with the charger on 50A so I reduce the output to approx 40A (75%). It's not long (30 mins or so if I start charging at 60% soc on the Smartgauge) before the current drops below the 40A showing that at this point the charger is producing as much as it would if it were set at 100%.

 

Getting back more closely to the point. The Adverc does lift the charging rate which is good but how good is debatable and does the battery care thing as well. Again is this necessary and is it worth the £200 or so that I paid for it? I've got it now and it does what it says on the tin.

 

Nick

Pretty much in line with my thoughts Nick. I think a lot of folk get suckered in thinking they'll cut their charge times by two thirds or whatever when the reality is that it won't save a whole stack of time at all.

[j04n]

Pretty much in line with my thoughts Nick. I think a lot of folk get suckered in thinking they'll cut their charge times by two thirds or whatever when the reality is that it won't save a whole stack of time at all.

5 times faster they quote, or even 20!! ....... mind it should be for that price! ......... surely it does something for £374?.......or is this to counter problems with these so called smart alternators?

 

http://sterling-power.com/collections/battery-to-battery-chargers/products/battery-to-battery-chargers

 

 

Edited October 12, 2016 by j04n

[WotEver]

........ surely it does something for £374?

 

I believe it might have pretty lights on the front.

[j04n]

I believe it might have pretty lights on the front.

oh well ......... i'll order 2!!!

[WotEver]

 

I suspect they are making a number of assumptions. That you only have a single alternator, that this alternator is small, that this alternator is wired to the engine battery, and that you use a diode split charge system. Even if all of the above were true they're all very simply addressed. Even if they weren't addressed I can't see where they get the 5x faster from.

[Tony Brooks]

Yeah but... have you noted how much time that actually saves? It'll undoubtedly save some time whilst the batteries are in bulk but how much? 30 minutes?

 

Tony

 

As long as the Adverc's raised voltage is higher than the alternator's regulated voltage it should also reduce the absolution time as well but because of the effects I pointed out I would have to say by how much. The Adverc's cycling is supposed to reduce gassing so it may be more efficient at charging that simply raising the voltage.

[WotEver]

 

As long as the Adverc's raised voltage is higher than the alternator's regulated voltage it should also reduce the absolution time as well but because of the effects I pointed out I would have to say by how much. The Adverc's cycling is supposed to reduce gassing so it may be more efficient at charging that simply raising the voltage.

Raising the voltage during absorption is unlikely to do anything more than increase gassing and evaporation and probably increase charging time. However, as you say, adapting the voltage, lowering it to the optimum as the charge progresses (how does it know?) could certainly reduce charging time.

 

As Gibbo explained it on here several years ago there is a constantly changing sweet spot voltage throughout absorption; higher voltage just increases gassing (which slows down charging due to the bubbles obstructing the plates) and lower voltage is simply sub-optimal. The problem is knowing what that voltage is, because it's not a simple curve. Maybe Adverc have spent some time in researching this phenomenon.

 

Tony

[ditchcrawler]

5 times faster they quote, or even 20!! ....... mind it should be for that price! ......... surely it does something for £374?.......or is this to counter problems with these so called smart alternators?

 

http://sterling-power.com/collections/battery-to-battery-chargers/products/battery-to-battery-chargers

 

But they are comparing it to your car split charge relay charging you caravan battery as you drive to the camp site. Far from an ideal charging set up, so maybe it is many times faster.

[dmr]

There is a theory, probably true, that increasing the voltage and hence current can increase charge times. More current goes to gassing and the bubbles act as a barrier between plates and electrolyte.

 

But if this was true then surely the likes of Trojan would be suggesting a charge voltage of 14.4, or even 14.2, rather than 14.8 ????

Using an Adverc to charge at 14.8 and sometimes 15.0 certainly works for me.

 

..............Dave

[dmr]

Mr Gibbo said (and therefore I believe it) that the above was so.

 

Note that (given long enough) 13.6V is quite sufficient to charge a battery to 100% and the battery will thank you for treating it so gently.

 

Tony

 

I don't know how to say this, and am certainly risking the wrath of the forum, or becoming branded as a complete idiot, but not everything that Gibbo said was actually true.

 

He was running a company that oddly marketed an alternator sharing device (Smartbank) as a direct competitor to alternator controllers (voltage raisers) such as the Adverc so it was not really surprising that he was a bit negative about increasing charge voltage. Even stranger, having said that voltage raising was not that important he went on to explain how to make a poor mans controller by putting diodes into the alternator sense lead.

 

...............Dave

[Keeping Up]

This ^^^ and a greeny. Gibbo's gave out a lot of useful advice but he wasn't God.

[dmr]

I suspect that for ordinary leisure batteries (as opposed to traction batteries), you won't gain much by charging a couple of points higher and would eventually shorten the battery life somewhat. Sure, 14.4V would be better but a 1.5% increase in voltage wouldn't make s huge difference.

 

What method do you use to determine the SoC of your bank?

 

Tony

 

Have we not done all this before? 14.2 to 14.4 is not a 1.5 increase in charging voltage, if we take the "charging voltage" as the voltage in excess of 12.8 (or thereabouts) then its more like a 14% increase.

 

.....................Dave

[nicknorman]

But if this was true then surely the likes of Trojan would be suggesting a charge voltage of 14.4, or even 14.2, rather than 14.8 ????

Using an Adverc to charge at 14.8 and sometimes 15.0 certainly works for me.

 

..............Dave

Trojan recommend a lower absorption voltage and then a higher finishing voltage. One interpretation would be that the former is to charge the batteries ASAP and the latter is to mix the electrolyte and remove any sulphation. Otherwise, why not just go for the higher voltage for the duration?

[nicknorman]

Even stranger, having said that voltage raising was not that important he went on to explain how to make a poor mans controller by putting diodes into the alternator sense lead.

 

...............Dave

I think it's a matter of context. If you have a 13.x v alternator charging via diodes, then clearly a means of increasing it is a good thing. If you have a 14.6v one charging direct, then probably not. The point is that there is an optimum voltage and thus, by definition, having more voltage is a bad thing. Otherwise we would be recommending to those with limited charging time to charge at 100v or whatever.

[dmr]

Trojan recommend a lower absorption voltage and then a higher finishing voltage. One interpretation would be that the former is to charge the batteries ASAP and the latter is to mix the electrolyte and remove any sulphation. Otherwise, why not just go for the higher voltage for the duration?

 

I need to think about this, an experiment would be good but doing battery charging experiments on a liveaboard boat could lead to domestic disharmony. US (or is it Crown) suggest a charging curve that goes right up to 16v (I think) so this is a sort of mini-equalise at the end of every charge so you could be right. Adverc do run their voltage cycle thing so maybe they already know this stuff????

 

...............Dave

[WotEver]

 

I don't know how to say this, and am certainly risking the wrath of the forum, or becoming branded as a complete idiot, but not everything that Gibbo said was actually true.

 

He was running a company that oddly marketed an alternator sharing device (Smartbank) as a direct competitor to alternator controllers (voltage raisers) such as the Adverc so it was not really surprising that he was a bit negative about increasing charge voltage. Even stranger, having said that voltage raising was not that important he went on to explain how to make a poor mans controller by putting diodes into the alternator sense lead.

 

...............Dave

I honestly don't see what Gibbo's SoC monitoring system has to do with a spat between him and Chris W. SmileyPete joined in too.

 

The argument went that there is an optimum voltage during absorption and that voltage changed throughout the absorption phase. That voltage will not be the same for all batteries (hence Trojan's (and Rollls) higher overall voltages). Below the optimum voltage you will be charging slower than necessary. Above the optimum voltage all you will be doing is electrolysing more water. As a by-product of the excessive gassing the bubbles start to create a barrier over the plates which actually decreases the charging.

 

Furthermore, higher voltages cause more plate shedding and internal corrosion.

 

It's simple enough to check. Discharge two ordinary leisure batteries to the same SoC then charge one at 14.4V and another at 14.6V and see how much the charge time changes.

 

As it happens I was only discussing this with Gibbo last month and he informed me that several companies had worked on advanced chargers that would attempt to track the optimum absorption voltage but their attempts were horrendously expensive and complex and required sensors within the battery cells.

 

I did say in a previous post that perhaps Adverc had done a lot of testing in this area and that their algorithm was an advancement. But that's very different to simply upping the absorption voltage.

 

Tony

 

But if this was true then surely the likes of Trojan would be suggesting a charge voltage of 14.4, or even 14.2, rather than 14.8 ????

Using an Adverc to charge at 14.8 and sometimes 15.0 certainly works for me.

 

..............Dave

Sure, Trojan like nice high voltages - that is closer to their optimal. Now try it with a cheaper battery.

[WotEver]

 

Some charging facts.

 

As the battery approaches full charge the specific density increases. Acid conducts electricity better than water. Therefore as the charge status increases the gassing voltage falls until it gets down to about 13.4 volts for a fully charged wet cell.

 

However, once a battery gets to about 95% charged, the remaining sulphate can be really difficult to remove. It can take days and days at a normal charge voltage. So that is why it is sometimes necessary to go to a much higher charge voltage than the ideal. Just to get rid of that last few percent.

[cuthound]

All battery charging is a compromise. For fixed installations, such as data centres, telecommunications etc, reliability and battery life are paramount, so batteries are charged at circa 2.3 volts per cell

at 25°C (13.8 volts). Anything above this reduces battery life by causing more shedding of the active material from the plates (which in extreme cases can short out plates thus causing cells to fail prematurely). However in practical terms, plate shedding isn't too much of an issue below about 14.6 volts.

 

For boating a 13.8 volt charge results in an unnecessarily long charge time, so higher voltages are used. Also the vibration causes plate material to be shed, and batteries are subject to wide temperature variations, so batteries won't last as long as they would in a temperature controlled environment to such as a data centre.

 

So it is all about compromise really.

 

Edited to correct autowrong induced errors.

Edited October 13, 2016 by cuthound

[WotEver]

All battery charging is a compromise.

Absolutely.

[dmr]

Trojan recommend a lower absorption voltage and then a higher finishing voltage. One interpretation would be that the former is to charge the batteries ASAP and the latter is to mix the electrolyte and remove any sulphation. Otherwise, why not just go for the higher voltage for the duration?

 

Right. The Trojan curve is pretty much a fixed voltage at 14.2 then once the charge current falls to 3% switch to a constant current regime till the voltage gets to a final value (maybe as high as 16).

Can your fancy charger do something like this?

It would be relatively easy to make an alternator controller to do this though it would need a current sensor. I will add this to my never ending list of electronic projects!!!.

So we need 14.2 volts to best charge a battery (maybe) but at least 14.8 to finish off/desulphate/stir things up. Trouble is for most boaters we never know how long the charging (cruising) is going to last so on short cruises we would never get to the finishing voltage. Hence its a case of choosing the lesser of two evils, charge at 14.2 and risk sulphation if we don't get enough finishing, or charge at 14.8 and live with a bit more plate shedding and even a slower charge rate (maybe).

I find it very interesting that the Adverc controller cycles between two voltages (14.4 and 14.8 in my case) so I suspect Adverc have already hit on a very good compromise between these two evils. (but they could do even better with a current sensor and little processor).

 

...............Dave

[nicknorman]

Right. The Trojan curve is pretty much a fixed voltage at 14.2 then once the charge current falls to 3% switch to a constant current regime till the voltage gets to a final value (maybe as high as 16).

Can your fancy charger do something like this?

It would be relatively easy to make an alternator controller to do this though it would need a current sensor. I will add this to my never ending list of electronic projects!!!.

So we need 14.2 volts to best charge a battery (maybe) but at least 14.8 to finish off/desulphate/stir things up. Trouble is for most boaters we never know how long the charging (cruising) is going to last so on short cruises we would never get to the finishing voltage. Hence its a case of choosing the lesser of two evils, charge at 14.2 and risk sulphation if we don't get enough finishing, or charge at 14.8 and live with a bit more plate shedding and even a slower charge rate (maybe).

I find it very interesting that the Adverc controller cycles between two voltages (14.4 and 14.8 in my case) so I suspect Adverc have already hit on a very good compromise between these two evils. (but they could do even better with a current sensor and little processor).

 

...............Dave

No the MV chargers don't do that specifically - although it could be achieved manually by adjusting the max voltage up and charge current down to give the "finishing" stage, once the batteries were nearly full. They do however make a reasonable compromise in the way they react to a high set changing voltage. The voltage under high and even moderate charging current doesn't really increase much, it is only near the end when the current has fallen right off that the voltage reaches it set high value.

[Theo]

I believe it might have pretty lights on the front.

 

No end of pretty lights. More pretty lights than you could shake a stick at. It works and I will have to put up with the fact that I might well have wasted a quantity of pension but there it is.

 

N

 

As long as the Adverc's raised voltage is higher than the alternator's regulated voltage it should also reduce the absolution time as well but because of the effects I pointed out I would have to say by how much. The Adverc's cycling is supposed to reduce gassing so it may be more efficient at charging that simply raising the voltage.

 

Does that mean that you can get away with less time in purgatory?

 

N

[ditchcrawler]

 

purgatory?

 

N

Is that sitting there running the engine just to charge the batteries?

[Theo]

Raising the voltage during absorption is unlikely to do anything more than increase gassing and evaporation and probably increase charging time. However, as you say, adapting the voltage, lowering it to the optimum as the charge progresses (how does it know?) could certainly reduce charging time.

 

As Gibbo explained it on here several years ago there is a constantly changing sweet spot voltage throughout absorption; higher voltage just increases gassing (which slows down charging due to the bubbles obstructing the plates) and lower voltage is simply sub-optimal. The problem is knowing what that voltage is, because it's not a simple curve. Maybe Adverc have spent some time in researching this phenomenon.

 

Tony

I don't think so, Tony. It's a simple change of voltage from 14.4V for five minutes and 13.9V for 15 minutes (IIRC) Ah! Here's the quote from the installation manual:

 

 

"The cycling programme is normally: 5 minutes @ 14.0 volts, followed by 15 minutes @ 14.4

volts. After four 20 minute cycles, there is a 'rest period' of up to 40 minutes i.e. at the lower

voltage, depending on the battery state-of-charge and electrical duty-cycle.

These voltage values lie either side of the battery gassing voltage, ensuring rapid charging

without the battery actually gassing. Voltage settings will accommodate most battery types

including gel. Ni-cads etc., require a special setting. The charging voltages will automatically

adjust for ambient temperature variations around the batteries, an important consideration e.g. a

voltage increase with cold ambient temperature and vice versa."

 

Where the Adverc is really useful for me is that it makes a much better job of upping the current produced by the alternator at lower voltages, ie when the battery is below about 80%.

 

N

Edited October 17, 2016 by Theo

[Theo]

 

Snip...

I find it very interesting that the Adverc controller cycles between two voltages (14.4 and 14.8 in my case) so I suspect Adverc have already hit on a very good compromise between these two evils. (but they could do even better with a current sensor and little processor).

 

...............Dave

 

I posted my last observations before reading the rest of the topic. This is a mistake. I would add here that the Adverc chooses its voltages according to temperature so the voltages stated in the quote from the manual must be frinstances rather that set values. This afternoon my Adverc was cycling between 14.4V and 13.9V. My batteries are in the engine hole under a cruiser stern so it must get pretty warm in there and the Adverc reduces the voltages accordingly.

 

Somewhat off topic, for which I apologise. when I was upgrading my 1983 Brum Tug soon after I had bought it ten years ago I replaced the 1, 2, both, off switch with Smartbank Advanced which interfaces Smartgauge with Smartbank to provide a bit more functionality. I always noticed that the Engine battery voltage as measured with the Smartgauge was always a bit higher than the domestic battery voltage, even with the relay contacts closed. I had always put this down to the Smartgauge not being accurate. It has only just occurred to me that this is because there is a voltage drop across the relay contacts. I have been watching the voltages much more carefully over the last weeks and notice that the higher the alternator current the bigger the difference. What a nelly!

 

N